1. Field of the Invention
The present invention generally relates to satellite broadcast receiving converters, and more specifically to a satellite broadcast receiving converter which is used to receive satellite broadcasts and satellite communications, and which receives circularly polarized waves having a vertical polarization component and a horizontal polarization component.
2. Description of the Related Art
Referring to FIGS. 10 to 13, there is shown a conventional satellite broadcast receiving converter. FIG. 10 is a perspective view of the converter, and FIG. 11 is a sectional view thereof taken along such a line XIxe2x80x94XI of FIG. 10. FIG. 12 is a partially enlarged view of the converter, showing how a probe is installed. FIG. 13 is a partially enlarged view of the converter, showing a circuit board mounted therein.
A housing 31 and a waveguide 32 are manufactured by die-casting with a metal such as aluminum or zinc and then forming the components into one unit. The housing 31 is formed into a substantially rectangular box, including a bottom wall 31a, side walls 31b that are vertical and which surround the bottom wall 31a, a housing portion 31c that is uncovered and is defined by the side walls 31b, a penetrating hole 31d formed in the bottom wall 31a in the vicinity of one end thereof and extending perpendicularly thereto, and a stepped portion 31e having a step along an upper periphery of the side walls 31b. The waveguide 32 is a relatively narrow cylinder, extending from the bottom wall 31a at a position corresponding to the penetrating hole 31d. The waveguide 32 includes a substantially cylindrical tube section 32b having an opening 32a from which polarized waves are guided, a hollow 32c formed lengthwise at the center of the tube section 32b, and a holder portion 32d. The holder portion 32d is a semi-columnar recess, as shown in FIG. 12, which is formed in the tube section 32b to extend toward the opening 32a from a portion of the periphery of the penetrating hole 31d of the housing 31.
A probe 33 for detecting horizontally polarized waves is composed of a tubular insulator 33a made of resin such as fluorine resin, polyethylene, or Teflon, and a linear core conductor 33b passing through the insulator 33a at the center thereof and mainly made of a metal such as brass or nickel. The core conductor 33b is formed into substantially an L-shape, leading to a first end 33c while the other end thereof, namely a second end 33d, is formed at the tip of the straight part.
Referring to FIG. 12, the insulator 33a is forced into the holder portion 32d in the waveguide 32, allowing the probe 33 to be installed into the waveguide 32. Once the probe 33 has been installed, the second end 33d of the core conductor 33b protrudes into the housing portion 31c of the housing 31 while the first end 33c extends into the hollow 32c of the waveguide 32.
In FIG. 13, there is shown a rectangular circuit board 34 formed of a single insulating sheet. The circuit board 34 includes a thin flat plate 34a, three penetrating holes 34b formed in the vicinity of a side edge of the plate 34a and extending perpendicularly thereto, bridges 34d and 34e defining the penetrating holes 34b to form a T-shape, and a small opening 34c formed in the vicinity of the penetrating holes 34b. A copper ground conductor 35 is formed on the underside of the circuit board 34 except for the underside of the bridge 34e, and the underside of the bridge 34d serves as a short-circuit for the probe 33.
A probe 36 for detecting vertically polarized waves is formed across the bridge 34e with a conductive pattern, and extends from the intersection of the bridges 34d and 34e toward the plate 34a of the circuit board 34. In turn, the probe 36 is connected to a circuit pattern (not shown) formed on the top of the plate 34a. The circuit board 34 is contained on the bottom wall 31a of the housing 31 so that the penetrating hole 31d may communicate with the penetrating holes 34b in the plate 34a. Also, the second end 33d of the core conductor 33b of the probe 33 is inserted in the opening 34c in the plate 34a, and the circuit board 34 is then fixed to the bottom wall 31a of the housing 31 by any appropriate means. The second end 33d of the core conductor 33b that protrudes from the circuit board 34 is soldered by a solder 37 to the circuit pattern.
A box-shaped metallic short-circuit wall 38 is formed by aluminum or zinc die-casting. The short-circuit wall 38 is mounted to the circuit board 34 by an appropriate technique such as caulking so as to cover the penetrating holes 34b in the circuit board 34. The short-circuit wall 38 has a base 38a acting as a short-circuit for the probe 36.
A cover 39 formed of a single rectangular metal sheet is placed on the step 31e of the side walls 31b of the housing 31, and is fixed thereto by an appropriate technique. Accordingly, the housing portion 31c of the housing 31 is closed and electrically shielded.
Such a conventional satellite broadcast receiving converter is of the type in which the housing 31 and the waveguide 32 are manufactured by die-casting such as aluminum die-casting and then forming the components into one unit. Therefore, a large number of materials are required, resulting in increased material costs as well as prolonged manufacturing time. This makes the converter expensive and less efficient in production.
In addition, the following problem also occurs with such a conventional satellite broadcast receiving converter. The housing 31 and the waveguide 32 have different sizes and configurations, and therefore more complex and expensive die-casting molds are required. This also makes the converter more expensive.
Accordingly, it is an object of the present invention to provide a satellite broadcast receiving converter which has superior production efficiency and is inexpensive.
To this end, a satellite broadcast receiving converter according to the present invention has a metal housing formed into a box, a tubular waveguide, and a box-shaped short-circuit wall which opposes the waveguide so as to communicate with a hollow formed in the waveguide, wherein the housing, the waveguide, and the short-circuit wall are joined together on a single metal sheet. These components are stamped out of the metal sheet, and then folded. With this feature, the number of materials making up the converter can be reduced. A simple manufacturing process as well as shortened manufacturing time can also be obtained.
The converter may include a circuit board on which an electric circuit is formed, wherein the circuit board is held by and between the housing and an end of the waveguide. This enables the circuit board to be held therebetween in a simple manner.
Preferably, the waveguide includes a hooking tab at a free-end edge of the end thereof, which is engaged with the circuit board. The use of a hooking tab ensures that the waveguide is mounted and positioned to the circuit board in a simple manner.
Preferably, a folding guide line is formed in a joining portion joining the housing with the waveguide, and the folding guide line may include cuts. The folding guide line facilitates folding of the waveguide at a predetermined position, so that the circuit board can be easily mounted to the waveguide.
Accordingly, the present invention provides for a satellite broadcast receiving converter with a simple configuration having high production efficiency as well as high reliability. There is no need for an expensive die-casting mold, so that an inexpensive satellite broadcast receiving converter can be obtained.